Material handling device



Feb. 22, 1955 J. F. FISHER 2,702,643

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MATERIAL HANDLING DEVICE John Farley Fisher, Manheim, Pa., assignor to Hershey Machine & Foundry Company, Manheim, Pa., a corporation of Pennsylvania Application June 28, 1950, Serial No. 170,925

3 Claims. (Cl. 214-1816) This invention relates to material handling devices wherein the material is fed or discharged over a substantial area at a constant rate or in measured quant1t1es.

There are many instances in which it is desirable that the feed of material not only be uniform over a substantial area, but also that means be provided whereby the rate of feed, while being accurately controlled, may be varied to meet specific operational conditions. For example, in fuel stokers it has been proposed to feed the fuel to the combustion zone of a furnace by causing it to overflow or spill over the sides of a distribution chamber or trough to which the fuel is supplied by screws rotating in the bottom of the distribution chamber. In such a stoker the fuel should be caused to flow over, or to be discharged onto the grate of the furnace in a layer of even depth throughout the length of the distribution chamber in order that uniform burning of the fuel will take place. If the fuel is not fed in a layer of substantially-uniform thickness onto the furnace grate an uneven burning will result, and unburned fuel will be discharged from that part of the combustion zone to which the fuel is supplied in a thicker layer, while in that part of the combustion zone to which the fuel is supplied in a thinner layer the fuel will be completely burned in too short a time and the grate area in that part of the combustion zone will not be fully utilized. A further disadvantage of non-uniform feeding of fuel to a furnace grate results in an uneven burning of the fuel in that in those places where the layer of fuel is thicker, less combustion air will pass therethrough, tending to form a dead spot, while at those places where the layer of fuel is thinner, combustion air will pass through the fuel at an undesirably rapid rate and cause a too rapid combustion of the fuel.

The feeding of material from a distribution chamber or the like in a uniform layer is also desirable for spreading rock or other material in the building of highways, it}( the feeding of material to shaker conveyors, and the li e.

The present invention is directed to the provision of a material feeding mechanism which will enable the material to be fed or discharged from a distribution chamber or trough in a uniform layer, and more particularly to such a material feeding mechanism which may be accurately controlled to feed or discharge desired amounts of the material, according to existing operational demands. In the broader aspects of the invention, the material feeding mechanism comprises a distribution chamber or the like to which the material is supplied by a feed screw and in which a substantially uniform depth or head of material is maintained throughout the length of the distribution chamber by circulating the material therein. Thus, a uniform discharge of the material will take place. On the other hand, if the material were merely fed to the distribution chamber at one end and a screw conveyor relied upon to evenly distribute it throughout the length of the distribution chamber, the material would not be fed or discharged from the distribution chamber in a layer of uniform thickness throughout the length thereof.

In order to obtain the necessary circulation of the material within the distribution chamber, the distribution chamber is provided with two longitudinally-extending screw conveyors having the same pitch and direction of pitch, but rotating in opposite directions, and positioned at opposite sides of the distribution chamber. One of the screw conveyors receives the material from a supply United States Patent 2,702,643 Patented Feb. 22, 1955 hopper and conveys it along the distribution chamber. When the chamber has received an amount of the material determined by the volume of the chamber, the screw .conveyor rotating in the opposite direction will pick up the material and convey it along the chamber in the op- (posite direction, thereby producing a circulation of the material lengthwise of the chamber and maintaining the material therein at a constant depth or head. The second screw conveyor may be separately connected to the supply hopper for returning excess material thereto or it may merely return the material to the entrance end of the distribution chamber. In the latter case, the return material again will be picked up by the first screw and the circulation of the material continued without any of it being returned to the supply hopper.

When the device of the invention is embodied in a fuel stoker, it preferably is extended the complete length of the grate bars and is positioned to one side of the combustion chamber of the furnace where it will be less affected by the heat of combustion and where any repairs or replacements of any of the parts may be made from outside the furnace, and without disturbing the fuel bed or taking the furnace out of operation.

It is preferred in many installations, such as in a fuel stoker, to provide positive feed means in the form of power-driven reciprocating-plungers for discharging the fuel from the distribution chamber into the furnace. In such a case the plungers extend transversely of the distribution chamber and engage a charge of the fuel from the chamber and push it onto the furnace grates, or onto a dead plate between the distribution chamber and the grate bars. In the latter case, each charge subsequently is pushed by succeeding charges onto and across the grate bars, and finally into an ash pit at the other side of the grate bars. Means are provided for adjusting the stroke of the plungers so that a charge of predetermined size can be forced into the furnace at each stroke of the plunger. A plurality of the plungers are arranged lengthwise of the distribution chamber and, collectively, cause a layer of fuel of uniform thickness to be shoved onto and across the grate bars. Combustion of the fuel takes place as it is pushed across the grate bars. As the fuel moves across the grate bars in a layer of substantially uniform thickness, combustion of the fuel in the moving layer will be uniform. The rate of feed of the fuel across the grate and the supply of air can be regulated to meet the demands of the furnace at any time, and yet insure maximum utilization of the grate area and complete burning of the fuel before it is discharged from the opposite side of the grate into the ash pit.

Each stoker unit may be made of a standard size and capacity and provision made whereby the units may be connected together to supply, from a single supply hopper, sufiicient fuel to increase the capacity of the stoker to the capacity of the furnace, if the furnace requirements are greater than the capacity of a single unit. This enables the factory production schedules to be set for only one size unit, and, where the stoker requirements are greater than that of a single unit, the stoker may be assembled in the field from a sufiicient number of the units to meet the capacity of any particular furnace. A further advantage of having a complete stoker assembled from a number of like units is that if any particular unit needs repair or replacement of any of the parts thereof, it is only necessary to remove that particular unit and replace it with another unit. That may be done in a relatively short time and with a minimum alteration of the furnace.

For a better understanding of the invention, reference is made to the accompanying drawings, in which:

Fig. l is a prospective view, partly in section, of a multiple-unit fuel stoker embodying the invention;

Fig. 2 is a schematic top plan view, partly in section of the distribution chamber and one of the stoker units of Fig. 1, with the top cover plate removed from the distribution chamber;

Fig. 3 is an elevational view of the driving means for the several parts of the stoker;

Fig. 4 is an elevational view of the driving means taken at right angles to Fig. 3;

Fig. is a horizontal sectional view along line 55 of Fig. 6;

Fig. 6 is a side elevation of the distribution section of one of the units of the stoker of Fig. 1;

Fig. 7 is an end view of the distribution section of the apparatus of Fig. 1;

Fig. 8 is a vertical sectional view on line 8-8 of Fig. 6;

Fig. 9 is a vertical sectional view on line 9-9 of Fig. 6;

Fig. 10 is a sectional view as shown in Fig. 5 but consisting of two stoker units.

Referring to the drawings and first to Fig. 2, the mater al-feeding mechanism comprises an elongated distribution chamber 32 connected at one end by a pair of conveylng tubes 33 and 34 to a material-supply hopper 31. A pair of screw conveyors 35 and 36 extend lengthwise of the distribution chamber, one along each side thereof, and through the conveying tubes 33 and 34 into the lower portion of the supply hopper. One end of each of the shafts of the screw conveyors is journaled at the end of the distribution chamber remote from the supply hopper and their other ends extend through bearings at the far side of the supply hopper.

The flight of screw conveyor 35 extends entirely across the supply hopper but terminates short of the end of the distribution chamber 32 remote from the supply hopper. The flight of screw conveyor 36 terminates at one end just inside the supply hopper, but its other end extends to the remote end of the distribution chamber.

The flights of screw conveyors 35 and 36 are of the same size and have the same pitch and same direction of pitch. Screw conveyor 36 is driven from screw conveyor 35 through meshing spur gears 54 and 53 mounted on their respective shafts. Consequently, when power is applied to the shaft of one of the screw conveyors the other screw conveyor will be driven from it and the two screw conveyors will rotate in opposite directions.

All of the operating parts of the said mechanism are drlven from a main power transmission 46. The power mput for the transmission may be furnished by a prime mover of any suitable type, such as an electric motor 47. The shaft of the motor 47 is connected through a belt 48 to a pulley on the end of the power input shaft of the transmission. An idler pulley 49 maintains the belt 48 in proper tension.

The end of the shaft of screw conveyor 35 extends beyond the spur gear 53 thereon and has a driving sprocket 51 fixed thereto. The sprocket 51 is driven from the main power transmission 46 through a chain sprocket and connecting sprocket chain 52.

The shaft of screw conveyor 35 is driven in a direction to cause that screw conveyor to rotate in a direction to feed material from the fuel supply hopper through the tube 33 into and along one side of the distribution chamber 32 to the remote end thereof. Screw conveyor 36 which rotates in the opposite direction. picks up material from the remote end of the distribution chamber and moves it back along the other side thereof, through the conveyor tube 34 and back into the supply hopper. Thus. the material is constantly circulated through the distribution chamber and is maintained therein at a uniform level and under a uniform head. Whenever any material is removed from the distribution chamber. it immediately is replaced by the screw conveyor 35, but if no material is being removed, all excess material conveyed into the distribution chamber by the screw conveyor 35 will be returned to the supply hopper by the screw conveyor 36.

In Fig. l, the fuel-feeding mechanism is shown as a stoker comprising a plurality of like units 29 connected together to form an elongated distribution chamber from which fuel is fed to the furnace. The distribution chamber is positioned to one side of the combustion chamber where it is less affected by the heat of the furnace and where repairs to it or replacement of parts may be made without disturbing the fuel bed or putting the furnace out of operation. To further protect the fuel within the distribution chamber from the heat of the furnace, an air chamber 55 is positioned between the distribution chamber and the combustion zone of the furnace. One end of the chamber 55 is provided with an air-intake opening 56 and the side wall of the chamber facing the combustion zone of the furnace is provided with a series of exhaust ports 57. Air for dissipating heat from the chamber enters it through the intake opening 56 and is discharged therefrom through exhaust ports 57 into the combustion chamber of the furnace where it acts as secondary air for combustion of the fuel.

The means for feeding the fuel from the distribution chamber into the combustion zone of the furnace is best shown in Figs. 6 to 9. As there shown, the lower wall of the distribtuion chamber, at the edge thereof nearest the combustion chamber of the furnace, is provided with a plurality of longitudinally-spaced openings 38 through which the fuel, under the uniform head thereof in the distribution chamber, falls onto a receiving plate 38. A plurality of plungers 37, two for each stoker unit, are mounted directly beneath the distribution chamber for reciprocation horizontally and transversely thereof and across the receiving plate 38 onto which the fuel is discharged from the distribution chamber. The plungers 37 act as both a means for controlling the discharge of fuel from the distribution chamber and for forcing the fuel into the furnace, across the grate thereof and into an ash pit on the opposite side of the grate.

When the plungers are in their retracted position, as shown in Figs. 8 and 9, the discharge openings 38 are uncovered and fuel will flow from the distribution chamber and be deposited onto the receiving plate 38 in front of the plungers. As the distribution chamber is maintained full throughout the length thereof and the material is under a constant head, the same amount of fuel will be deposited in front of each plunger as long as the stroke of the plungers are adjusted to be the same.

As the plungers move forwardly, their upper surfaces close the discharge openings 38 to prevent further flow of fuel through them. On their forward movement, the plungers push the fuel from the receiving plate 38' onto a dead plate 39 positioned between the plate 38' and the furnace grate 41. As the plungers continue to operate, the several charges will progressively be pushed by succeeding charges across the dead plate 39, onto the grate bars and finally across a dead plate 40 at the opposite side of the grate and into an ash pit at the far side of the plate 40.

A plenum chamber 42 is positioned beneath the grate bars 41 for supplying air for combustion of the fuel. Air enters the plenum chamber at one end through an opening 43 and passes upwardly through the grate bars and the fuel as the latter is progressively moved across the grate bars under the action of the plungers 37.

As the fuel moves across the grate bars in a layer of substantially uniform thickness, the resistance to the passage of air will be the same throughout the fuel bed and uniform burning of the fuel will take place without the formation of dead spots. Also, if the rate of air injection into the plenum chamber is properly correlated with the rate of feed of the fuel onto and across the grate bars, completeness of the burning of the fuel can be obtained just prior to the discharge of the ash into the ash pit, thereby obtaining the maximum use of the entire grate surface without the discharge of unburned fuel into the ash pit.

Power for imparting reciprocatory movement to the plungers 37 is taken from the main transmission 46 from a shaft 58 having a chain sprocket 58 secured to its outer end.

A power-transmitting shaft 59 extends lengthwise of the stoker beneath the distribution chamber 32 and the plungers 37. The shaft 59 is mounted in suitable bearings on the base of the stoker frame and has a chain sprocket 60 non-rotatably secured thereon at one end. A chain 61 passes around sprockets 58' and 60 and transmits power from the shaft 58 to the power-transmitting shaft 59.

A crankshaft 63 for operating the plungers 37 of each stoker unit is journaled in bearing 63' depending from the underside of the receiving plate 38'. Each of the crankshafts 63 has a chain sprocket 64 fixed thereon which is driven from a sprocket 62 on the power-transmitting shaft 59 through a chain 65.

Each of the crankshafts has a crank 68 for each plunger to be actuated. A connecting rod 67 has one end thereof journaled in each of the cranks 66. The other end of the connecting rods are pivotally connected at a midpoint of a plunger-actuating link 68. The lower end of each link 68 is bifurcated and straddles and is pivotally connected to-a bearing boss 69 on the frame base. The upper end of each actuating link 68 likewise is bifurcated and each arm of the bifurcated portion is provided with an openended slot 68' which receives a trunion 70 extending from opposite sides of a block 70 movable along a threaded plunger shaft 71 mounted in and extending rearwardly from a cross member 37 of each of the plungers 37. Each block 70' is movable along its plunger shaft 71 between the rear face of the cross member 37' and a set of nuts 72 which may be adjusted along the shaft 71 to limit the extent of travel of the block away from the cross member 37.

Rotation of the crankshaft 63 causes a reciprocation of the connecting rods 67 and a corresponding swinging of the upper portion of the plunger-actuating links 68 backwardly and forwardly. The swinging movement of the upper end of the links 68 causes the blocks 70' to be reciprocated along the plunger shaft 71. As the upper end of each link swings forwardly, that is, towards the combustion chamber of the furnace, the block slides along the shaft 71 until its forward face engages the rear face of the cross member 37. Further movement of the upper end of the link 68 and the block 70 then causes the plunger to move forwardly and to push a charge of the fuel deposited on the receiving plate 38 forwardly onto the dead plate 39, as heretofore described. As the upper end of each link 68 swings back, the block 70' journaled therein first moves freely along the plunger shaft 71 until the rear face of the block engages the adjusting nut 72. Further backward movement of the upper end of the link 68 then retracts the plunger to the position shown in Fig. 14 to permit another charge of fuel to be deposited onto the receiving plate 38 to be pushed into the combustion zone of the furnace on the next forward stroke of the plunger.

By adjusting the position of the nut 72 along the plunger shafts 71, the length of the strokes of the respective plungers may be regulated and a charge of fuel of any desired size discharged from the distribution chamber and pushed into the furnace on each stroke of the plunger.

The cranks 66 for each stroker unit extend from the crankshaft 63 in opposite directions, or 180 out of phase, in order to better balance the forces on the crankshaft. With the cranks so mounted, one plunger of any unit will be moving forwardly on a charging stroke, while the other plunger of the unit will be moving to its retracted position.

The manner in which the stoker units may be assembled when a stoker of a capacity greater than a single unit is required is shown in Fig. 10. In this case, one or both ends of each distribution chamber is formed with a pair r of aligned openings, depending upon whether the distribution chamber is to be joined at one or both ends to a like distribution chamber. Distribution chambers are abutted in end-to-end relationship with the openings in alignment and the several distribution chambers secured to one another in any desired manner. Conveying tubes 77 and 78 are welded or otherwise secured in the aligned openings to permit passage of fuel from one distribution chamber to the next adjoining one. The shafts of the screw conveyors 35 and 36 are connected to the shafts of screw conveyors 35a and 36a of the next adjacent distribution chamber by couplings 76 to provide continuous screw conveyors extending the full length of the connected distribution chambers and through the conveyor tubes 77 and 78. With the several sections of the stoker thus connected, the screw conveyors 35, 35a will convey the fuel first throughout the length of the distribution chamber 32, and then through the tube 77 into the connected distribution chamber 32a.

The screw conveyors 36, 360 will pick up the material from the far end of distribution chamber 32a and carry it back along the opposite side thereof, through the conveyor tube 78 and into and along the distribution chamber 32. In this way, the fuel may be continuously circulated throughout as many connected distribution chambers as may be desired, and a uniform level or head of the fuel will be maintained in all of them, it only being necessary that the conveying capacity of the several screw conveyors be greater than the capacity of the plungers 37 to force the fuel into the combustion chamber of the furnace.

The air chambers 55 also are connected through aligned openings 56 so that cooling air may be forced throughout the length of the connected chambers.

The electric motor 47 of the main power unit 30 will be electrically connected to the automatic control circuit of the furnace, normally a thermostatic-combustion air control, so that upon energization of the motor the stoker will be put into operation.

The operation of the apparatus will be generally apparent from the foregoing. The fuel is removed from supply hopper 31 and pushed through the conveyor tube 33 by the rotation of the conveyor screw 35 where it is discharged into and moved along one edge of the distribution chamber 32. As the conveyor screw 35 fills the distribution chamber to its designed capacity of fuel, the conveyor screw 36 will return the excess amount of fuel through the conveyor tube 34 back into the supply hopper 31. A constant amount of fuel, and, therefore, a constant head of fuel, is maintained in the distribution chamber 32 at all times, with any fuel being removed from the distribution chamber being immediately replaced by the conveyor screw 35. When the plungers are in their retracted position, fuel will be discharged from the distribution chamber through the openings 38 and deposited on the plate 38 in front of the plungers. As the plunger moves forward on its injection stroke, it closes the opening against further discharge of fuel therethrough and pushes the fuel already deposited onto the plate 38' in front of it into the furnace. After the plunger 37 has reached its full extended position and begins its retracting stroke, the deposit of fuel is left on the dead plate 39. Each charge of fuel moved on the dead plate 39 moves a previous charge of the fuel further across the plate and onto the grate bars 41 where combustion takes place. In a like manner, the fuel is progressively moved by subsequent charges across the grate bars, this movement continuing until the fuel is burned and the resulting ash shoved across the dead plate 40 and into the ash pit at the far side thereof.

Should it become necessary to increase or decrease the charge of fuel introduced into the furnace on each stroke of the plungers 37, this can be accomplished by appropriately adjusting the position of the adjusting nuts 72 on the shaft 71, the length of stroke of the plunger being directly proportional to the distance between the adjusting nuts and the rear face of the cross member 37 I claim:

1. A material handling device comprising a supply hopper, a material distribution chamber connected to the supply hopper at one side thereof to receive material therefrom, a screw conveyor extending from within the supply hopper into and along the distribution chamber to receive material from the supply hopper for conveying to the distribution chamber, means for actuating said screw conveyor to move material from the supply hopper and in one direction along the distribution chamber, a second screw conveyor positioned within the distribution chamber, said screw conveyors being arranged in said distribution chamber in substantially horizontal parallel relationship, means for actuating said second screw conveyor to move material in the distribution chamber in a direction reverse from that in which it is moved by said first screw conveyor, whereby material fed to the distribution chamber by the first screw conveyor will be circulated in the distribution chamber, said second screw conveyor being connected to the supply hopper for returning excess material thereto, the actuation of said screw conveyors uniformly distributing the material throughout the distribution chamber and maintaining it at a substantially uniform level and at a substantially uniform head therein, said-distribution chamber having a discharge opening in the bottom thereof through which material may be discharged, a surface positioned beneath said opening to receive material discharged therethrough, and a plunger mounted for reciprocating movement horizontally over said surface beneath said opening and transversely of the distribution chamber for removing material deposited on said surface, said plunger cooperating with said opening to close the same on its forward stroke.

2. A material handling device as set forth in claim 1 which includes means for adjusting the retraction stroke of the plunger to regulate the extent to which the plunger uncovers said opening on its retraction stroke.

3. A material handling device as set forth in claim 2 in which the means for adjusting the retraction stroke of the plunger comprises a threaded shaft extending rearwardly from a portion of the plunger, an adjusting nut threaded on said shaft, a member slidable on said shaft between said adjusting nut and said plunger portion and 7 having a trunnion extending therefrom, an actuating lever 1,209,597 engaging said trunnion, and means for actuating said lever. References Cited in the file of this patent 1:572:945 UNITED STATES PATENTS 'gig'gji 233,324 Caldwell Oct. 19, 1880 2,034,099 333,965 Moore Jan. 5, 1886 2,406,886 1,054,464 Soucek Feb. 25, 1913 2,489,801 1,193,016 Heyl Aug. 1, 1916 10 2,570,864

8 Lassiter Dec. 19, 1916 Mathews June 12, 1923 Himmelsbach Apr 22, 1924 McBean Sept. 3, 1946 Myott Nov. 29, 1949 Rowlson Oct. 9, 1951 

